Drive units having a drive train as described, utilizing a turbocoupling, initially should permit the generation of a high speed by the drive motor, for example an electric motor, with the turbocoupling empty. Upon attainment of the nominal speed of the drive motor, the turbocoupling is filled with its liquid medium, for example oil or water, and enables smooth startup and startup under load of the machine.
The control of the degree of filling of the turbocoupling, as has been noted above, affects the delivered torque and thus the operating state of the drive train. However, a hard blockage of the driven part of the system, i.e. the transmission of the driven element which receives the torque from the turbocoupling can cause on the one hand a delay in fuel-torque transmission between the turbine wheel and the pump wheel, i.e. the driven rotor and the impeller rotor of the fluid coupling to compensate for the blockage and, on the other hand, significant dynamic effects on the fly wheel mass forming the turbine rotor which can be detrimental. As a consequence the overload on the turbocoupling must be removed as quickly as possible in the event of such a hard blockage and in practice, load removal by emptying of the fluid coupling can only be done with a certain time delay. This, of course, can be detrimental to the mining machine or conveyor. For example, the chain may break and, in that case, it is important that the drive motor be decoupled rapidly from the transmission so that the run-out of the chain ends does not occur, thereby delaying repair. Furthermore, upon generation of an emergency signal, the mining machine or conveyor must be shut down immediately and that is not possible with conventional designs of the drive unit for such machines.